I would suggest not using a stone if your having issues finding any pet. Just pass that one for the time being and move on. Then you can camp on an alt, and check once in a while. Once you have everything else tamed, you can go back to it. The Giraffe took me over a week of non stop camping to find a rare. They are out there, just have to be very patient. Don't forget, some pets can not be found as rares. Save your stones for those.